pwmout freq

hippy

Technical Support
Staff member
Do let us know how you get on.

I've never tried this, but one issue I'd been concerned with has been how to do the control switching fast enough; using PWMOUT to switch the signal on and off might not give the timing accuracy needed as a result of PICAXE instruction timing.

Using PULSOUT to a control pin would allow an external 555-style modulator to be used and make it easier to generate correct pulse lengths ( and a PULSOUT to a dummy, unconnected pin allows the gap timing to be done ). To use this technique with PWMOUT would require some external logic, however, you may be able to get away with using just a few signal diodes ...

http://homepage.ntlworld.com/the.happy.hippy/picaxe/irmod.txt

The logic is inverted; keep CONTROL high to disable the signal, low to enable it. When either PWMOUT or CONTROL is high, there will be no positive voltage drop across the IR LED so it will be off, but when both are low the IR LED should 'light up'.
 

ANJ

Senior Member
Another way do do this is to use a constant PWM output through an current control resistor, with a pulldown diode on the line going back to a control pin. The pulldown goes between the inline resistor and the IR LED.
By using this mechanism, the only timedelay is in the on/off of a pin, not the start/stop of the pwm. If you can control yr basic port timings well enough to drive an external 555 you can control the port well enough to do this method.
Andrew
 
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